Bump actions/cache from 5 to 6

Bumps [actions/cache](https://github.com/actions/cache) from 5 to 6.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v5...v6)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/documenter.yml

@@ -21,7 +21,7 @@ jobs:
         uses: julia-actions/cache@v3
       - name: Cache Quarto
         id: cache-quarto
-        uses: actions/cache@v5
+        uses: actions/cache@v6
         env:
           cache-name: cache-quarto
         with:
@@ -31,7 +31,7 @@ jobs:
             ${{ runner.os }}-${{ env.cache-name }}-
       - name: Cache Documenter
         id: cache-documenter
-        uses: actions/cache@v5
+        uses: actions/cache@v6
         env:
           cache-name: cache-documenter
         with: